1985 300SD help
 

A while back my odometer stopped working as well. I ordered replacement gears from odometergears.com, installed them and it worked OK for a while.

Then it seemed it would work sometimes, then not work anymore. I inspected and lubed the gears a couple of times with no real change. Recently the odometer stopped working all togather. I found this thread and embarked on fixing mine as well.

The gears I installed were working just fine as I can sping them and the odometer moves fine, which makes me believe I have an electrical problem:

http://i440.photobucket.com/albums/q...ps74148938.jpg

Using some solder wick and a good iron, I unsoldered the five points that hold the speedometer to the unit:

http://i440.photobucket.com/albums/q...ps271babc6.jpg

I found this:

http://i440.photobucket.com/albums/q...ps1058bae4.jpg

Unlike the OP, my 85 300SD only has two capacitors. One I can clearly see as 220/6, the other one I can't make out for sure, but I beleive it is 1.7/16. Does this seem right. I know very little about these. I plan on picking some up at radio shack over lunch and putting this back togather.

Any good eyes here that can make out the numbers on the smaller cap?

http://i440.photobucket.com/albums/q...psd755c928.jpg


Thank you in advance!

To me it looks like 47, which would also make sense because that is what the others had, too.

RadioShack might work, but I liked the 105C ones I got from a real electronic shop. RadioShack has them online, unless you have a RadionShack with a huge selection nearby.

Hope that works!

I would guess 47 too.

I repaired an 86 300SDL speedometer and it had a 47 uF cap in it. 47 and 220.
W126 Speedometer Repair - Imgur

My '84 300SD only has two capacitors: a 220uF and a 47uF also. It looks like the markings on your capacitor are stamped off-center resulting in the side of the "4" not showing up. Funny, though, because it does look like a perfect "1".

Thanks for the confirmation on the numbers. I was able to pick up both caps during lunch, a 220 and a 47 uF 35w. I'll get them soldered in this afternoon and get a test drive this evening.

I do have some nice test equipment here at work and I am curious how the old ones measure when I get them out.

Hmmmm.


I got the new ones soldered in:

http://i440.photobucket.com/albums/q...psa6c93e10.jpg


I used these radioshack part numbers:

http://i440.photobucket.com/albums/q...psb3afcd71.jpg


I took the old ones, and with a BK precision 875B meter I found that both of the original caps measured pretty close to what they should be. The 220 uF cap measured 232 and the 47 uF cap measured 46.

I'll get this assembly back in the car this evening and hope for the best. If this does not get my odometer going, what is the next item that could be the culprit? I do have new gears and when I spin the drive gear with my fingers the odometer does move fine. Could the motor be bad? Can you replace that?

Well, odometer still does not work.



I'm open to any suggestions.


Sent from my Windows Phone

Is there an easy way to tell how to orient the capacitors? I assume, like a diode, the longer tail is positive?

Yes the longer lead on the capacitor is positive. On the short lead side there should be a white strip or arrow on the capacitor's body. This indicates the negative side of the capacitor. Generally the boards are labeled where + should go.

Dear JamesDean
I have a W126 280SE 1982 and my speedometer overestimates about 40%. I have changed 2 capacitors (it have only 2 caps 47 and 220) but problem did not resolved. all gears are in good health and the movement is smooth. please let me know your suggestions.
Thank you in advance.
Kamran

Hi, I just saw this now. Did you ever resolve this issue?

Hello Kamran,

Do you know if the gears are original or have they been replaced?

Do you know if your car's differential has been replaced? The odometer/speedometer are matched to the cars differential. 40% sounds like someone might have swapped the differential or instrument cluster? Is your speed accurate?

-Kris

not sure
 

Has this problem always been there??
A 280SE sounds like an EURO to me that at one time got federalized.
During the federalization process of mine, they build in a new speedometer.
If that is true for your's, too, maybe they didn't pick the right one?
The rear diff ratio could be different, leading to a wrong speed indication?
So maybe the gearing works, but you have the wrong gears....

Just an idea.

Definitely a possibility. I would get a GPS out and check the speedometer and see how accurate it is.

It might just be a case of the wrong gears on the odometer.

Hi
Unfortunately I don't know the previous history of the lady. But it is euro type.
How can I be sure about diff or trany?

I think the only way really is to physically inspect the trany/diff and get the part numbers off them.

Might also help if you got the part number off the speedometer/odometer unit too.

From there we could check it against the EPC and see if it is the proper parts or if they were replaced at some point in time, etc

Hi
My cluster S/N is 126 542 60 01
but could not go behind and check the trany/ diff.
could any one help me.
Is it possible changing capacitors with other cap may cause calibration?
Thanks

Hmm i could not find that part number in the Mercedes EPC. I'm not saying it does not exist, just that they don't have it in there..which is not uncommon.

Changing capacitors would not cause that large of a calibration error.

Does anyone know how many teeth I need to order for the 85MPH speedometer? Mine stopped counting the other day at 399,647. It pissed me off because I am waiting for it to roll over to 400,000. I'm not looking forward to pulling the cluster, opening it, counting the gear teeth, putting it all back in and doing the same thing again to swap the gears.

The gears from garagistic are only $17 - has anyone bought from this company?

I've never bought from them. I pretty much just buy from OdometerGears.com.

I had one customer that bought cheaper gears, maybe from the above company but I can't be sure. They were not as robust and one was the wrong size. Not saying the $17 ones won't work just sharing my experience.

I think you should just bite the bullet and pull the cluster.

Check out this photo album. I took these when I re-did my dad's 300SD clock and a buddy's 560SEL clock/tach.

W126 Odometer / Speedometer / Clock Repair - Imgur

EDIT: I took some notes when I repaired a customers 85 MPH speedometer.

http://www.odometergears.com/products/Mercedes-Benz/S+class+%28126%29++79-91+Diesel/53

Note my reference designations might not be equal to OdometerGears, check my drawing below:
E1 = 12
E2 = 48x12
E3 = 48x36
E4 = 48x12

http://i.imgur.com/LdLXjnWl.jpg

Instead of counting the teeth, just read the numbers on the gears. The number of teeth is marked on each gear. On the larger gears, the number has a "Z" in front of it. You'll see something like Z12 Z45. Sometimes reading those numbers is easier than counting a bunch of little teeth.

I grabbed one of my spare 85MPH clusters and took it apart to see that the 12 tooth gear has fallen apart. I did get one of the other gears out and the smaller inner section has 12 teeth. It looks like the other one like it had 12 teeth on the inner part as well. Is it safe to assume that MB did not change these parts over the years of the 85MPH speedo and that 12 tooth gears are what I need? If so, I will take a risk and order the $17 gears. If they suck eggs, I will let everyone know. If not, it may be a cheaper source for gears.

I don't see any markings on these gears. It looks like the plastic has sweat and may have destroyed any markings if they were there.

The markings are either engraved or cast, not printed. All the OEM gears I've come across have the markings. They're really tiny on the innermost white gear, but the others are a bit bigger. They're hard to see with all the lube/grease/grime on them, but the markings should be there. You may have to wipe them clean to see them.

This has been my experience as well. All of the factory gear should have numbers on them. If yours don't I would wonder if they were replaced at some point?

Gotcha. I see the markings on the gears made of harder plastic but I can't find any markings on the softer gears that I am replacing. Those gears seem to be blistered in a waxy substance that when scratched off, would remove a thin layer underneath. The gears are so malleable that I could split one in half with just my fingernail.

JamesDean,

Can you confirm that I bought the correct capacitors for the speedometer and clock? I'm not an expert by any means and the kids at Fry's knew less than I did. I saw uF and MF ratings and it confused the heck out of me. The box on one of them says 47MFD but on the cap, it says 47u@50V. The others seem to match your description.

Eaton,

MFD is another way of saying microfarads or uF. Those all look good to me. I don't remember the voltage specifications off hand but as long as your new cap's voltage is equal to OR higher than the old ones you'll be good!

Thanks for the quick reply! I feel confident that I have the correct parts now.

Hopefully by the end of the week I will have a full, in-depth, video series describing the odometer gear and capacitor replacement. The filming has been done and I am waiting for it to be edited.

560SEC speedometer repair
 

Hi folks just read this chatline and signed up for my 20 cents worth..

Just pulled the cluster from my Australian compliance 1989 560SEC - it was reading 100kph at a real roadspeed of 90kph (satnav check) - no wonder everyone was passing me on the freeway. The cluster has never been changed from new. Replacing the 2 capacitors made only a small difference. I've read a few blogs saying you cannot adjust the speed reading of these Mercedes digital speedometers.

I'm a bit of an electronics nut, so downloaded the data sheet for the drive chip (UAF2115), and found that you CAN adjust the speed reading on these instruments. The 750ohm resistor next to the chip on my PCB (see photo attached) is used to calibrate the meter reading on the dial. I removed it, extending some leads out to find the room to attach a 68ohm resister plus a 20ohm multi-turn precision trimmer. I can now adjust my speed reading by about +/- 15%.
http://www.peachparts.com/shopforum/attachments/tech-help/131236d1438234522-how-w126-odometer-repair-clock-capacitor-replace-560sec-speedo-1.jpg
I'm not convinced this is related to the REAL fault as I still have a linearity problem in this speedo so have more work to do (plus I have to design and 3D print a replacement odometer drive pinion (mine has split).

I'll make another post once I've cleaned up everything and am happy I've got a final solution.

My apologies for a very crude post - maybe I should just stick to electronics!!

I'm going from memory here on a good amount of this so bear with me.

I am fairly certain that resistor is used to configure the galvanometer current. Changing it will cause some linearity problems. I recall that from trying to make a 560 speedo head work for a 300SD.

OdometerGears.com sells replacement gears as does Garagetastic but 3D printing does sound fun so its all in how you wanna spend your time.

Aside from electronics, speed error could be introduced by wheel/tire sizes that are dramatically different from stock sizes. Are you tire/wheels stock or have you changed out?

Hi Dean
I'm new to this chat-line thing and still learning the ropes, but thanks for your comments. You make some good points I had not addressed.
Wheels and tyres are definitely NOT standard issue. Wheels are 16" Momo brand competition types with rims, 7" wide front and 8" on rear. Fitted tyres with rolling radius close to original Mercedes specification. Rear tyres were within +0.2% of original spec and they are currently 1/2 worn, so that wasn't the problem. My speedo error was +10% at 100kph (65mph). This was measured against my Uniden "Guardian Angel" GPS speed minder (designed to act as a speedometer), and very accurate on straight roads.
I had previously checked my odometer against highway markers and it came up spot on for distance, so I assumed it was not a sender problem.

You are 100% right about that resistor. According to the data sheet this resistor is provided to allow the auto manufacturer to compensate for calibration variations in individual speed meters. That would not work if it created serious non-linear effects. My resistor was marked 75.0ohms (an "odd" value), and measured 76.1ohms so it can't be causing the 10% error.

I now have the (adjustable) speedometer reassemble and on the test bench. It comes up as correct and linear all the way from 40kph through to 200kph, and only shows errors of 1-2 kph below 40 (not a problem).
Next step is to finish the cluster overhaul and get back out there on the road. Then I'll know the real truth.

I have no idea why you had such problems with your 300SD conversion. Is it possible the sensors are different? There ARE some components that effect the way the ITT chip "shapes" the sensor pulse-train before it is processed. Two of the resistors appear to provide a custom-trimmed value, and one of these appears to have been installed at Mercedes "assembly" time, not when VDO made the PCB. Can you remember if the other resisters and capacitors next to the chip were identical between the two instruments?

3D printed gear (12 tooth pinion) is fitted and works fine. Pattern now posted on Thingiverse. If the next gear in line lets go it'll be time to contact Pelican Parts, it would much easier than designing another.

Thanks for odometer tip
 

1988 190E 2.3, identical loose gear problem. Odometer sometimes ok on cold days, but really slips on warm days and numbers stand still. Purchased car recently and suspect actual mileage is much higher than indicated. Saw one suggestion using careful application of super glue, but didn't want to try that in such a closely fitted mechanism. Scoring the odometer shaft looked like a much better idea. Small conflict on chasing the shaft out with a drill bit. Rather than risk further disassembly, I filed a little notch in the odometer frame to allow axial access. See photo. #33 drill bit (0.113 inch) worked fine, just barely long enough at 2.75 inches.

Wasn't sure what sort of 'scoring' would work on the shaft, so I just took the vise-grips to it, figuring no material would be removed, merely rearranged. See photo. Evidently that was overkill, since aggressive tapping was required to force that deformed shaft back into the drive gear. Solid connection now.

Electric drill test looks good. I use a short length of 1/4-inch nylon zip-tie to couple the drill to the odometer cable fitting. Kind of loose and eccentric but not likely to do any damage (wear eye protection). My variable speed drill goes up to 75 mph (turning counter-clockwise). Real test will be an 800 mile road trip this weekend. I may finally get some valid miles-per-gallon data.

85 380SE nonworking speedometer, what to do?
 

You should be able to see the small board fastened to the clear gear cover. I'm guessing that cover needs to be removed to replace those gears.

Shall I buy a soldering station and 'unsolder,' those connections to replace the gears or am I missing something?

Been years since i did both SD's. But i do recall it was a purely mechanical repair only required fidgeting with the tiny axles and removing the melted and crumbling yellowed old gears to replace with the new.

No unsoldering anything unless the SE has a different setup.

What you see is what I have.
 

Like you, I remember doing my 84 SD by removing that clear, plastic cap on the gear end and changing the gears. It seemed quite simple though proved to be tedious to handle such small and delicate parts.

Here's another shot.

<img src="http://www.peachparts.com/shopforum/attachment.php?attachmentid=146452&stc=1&d=1517224392">

I soldered in 2 capacitors that I picked up from the local electronics shop. At first the clock only worked for 5min at a time. I noticed that I did not cut one of the leads short enough on the back side of the board and I'm guessing that capasitor was shorting out. Now the clock will keep perfect time as long as the ignition is on. Once the ignition is off I think the clock continues to run for around 4 hours before it stops. There have been various upgrades to the stereo system in the past. I am not stokum on electronics at all, so I'm wondering, does the power for the clock come directly from the battery, or do the capacitors power the clock when the ignition is off. Would they power the clock for 4 hours with no power at all. I'm thinking maybe someone in the past may have spliced wires behind the dash and the clock power is no longer continuous but should be.

To chime in on the odometer gears, I now have some experience that may help someone. I payed for the $65 set of gears, but suspect I could have gotten the same thing for $17 and not paid the middle man. The second thing I learned was, as far as the replacement gears go, the 2 new bigger gears should be riding on clean spindles. I cleaned with wd40 on a rag. The small gear in the package is the only one that needs to be secure on its spindle, it determines the rate all of the rest of the gears turn right up to the trip and odometer. I learned after gluing all gears and trying with dirty spindles, neither of which worked.

I, like you, suspect someone messed with your wiring in the dash. The clock should have 12V regardless of key position and should always keep time. The clock takes about 20mA of power every second. I think there is some 200uF of capacitance there.

I'd put a meter on that power line going the clock (spade terminal) and see if you've got 12V there with the key off.

--Kris

Hello,

I used in my 300 SL (R107) 2 Capacitors Elko 16 V, 100 Microfarad

Best regards
Marcel